Thermostat



March 22, 1960 G. BLOCH 2,929,901 manos'l-AT Filed lay 9. 1958 5Sheets-Sheet 2 Filed lay 9. 1958 5 Sheets-Sheet 3 Mmh 22, 1960 G. LQCH2,929,901

THERMOSTAT Filed lay 9. 1958 5 Sheets-Sheet 4 ."Ev- 8 "ff/8 fof? f2' G.BLOCH Tmuos'm March 22, 1960 Filed nay s, 1958 5 Sheets-Sheet 5 ffMaul/- United States Patent() 1 THERMOSTAT Gaston Bioch, Zurich,Switzerland, assigner to Firma Trafag Transformatorenban A.G., Zurich,Switzerland Application May 9, 1958, Serial No. 734,222 7 Claims. (Cl.ZOO-140)' According to their structure and action, the conventionalthermostats are mainly subdivided into rod thermostats with a metallicrod as temperature-sensitive member, bimetallic thermostats, evaporationthermostats working in the region of the saturated vapor of a fiuid, andiluid expansion thermostats utilizing the change in volume of a iiuidfor temperature regulation.

According to their fields of application, all the known thermostats havetheir advantages and disadvantages. Generally, rod thermostats are usedfor boilers and hot water storage, bimetallic thermostats for roomtemperature regulation, and evaporation or fluid expansion thermostatsfor regulation of industrial heating processes. This variety in designand action of the known thermostats renders their series productiondifficult and expensive. i

The present invention originated from the idea of creating a standardthermostat suitable for practically all purposes, which always works onthe same principle by employing identical and simple basic elements. Atthe same time, the thermostat should meet the most exacting demands asregards sensitivity and accuracy of response.

In accordance with the invention, the thermostat is characterized inthat it comprises at least one metallic resilient body at leastpartially filled with a lluid and subject to the thermal expansion ofthis fluid, a small tumbler switch which forms a separate structuralunit with an operating path of but a few hundredths of a millimeter, anda simple transmission lever transferring the movements of the resilientbody to the tripping pin of the tumbler switch.

The accompanying drawing shows by way of example some forms ofembodiment incorporating the invention.

Fig. l is a longitudinal section of a boiler thermostat of the tirstform of embodiment;

Fig. 2 is a plan view of the same thermostat;

Fig. 3 is a longitudinal section through a thermostat of a second formwith capillary tube for general industrial purposes;

Figs. 4 and 5 are sectional Views of two further forms, in which thetransmission lever is resiliently mounted, and not pivotally as in Figs.1-3;

'.Fig. 6 shows a fifth form of -a thermostat having two spring bello-ws;

Fig. 7 shows a sixth form of a double thermostat;

' Fig. 8 is a top plan view to Fig. 7;

Fig. 9 is a seventh form of another double thermostat;

Fig. l is a top plan view to Fig. 9.

Referring to said annexed drawing, the boiler thermostat according toFigs. l and 2 is constructed as follows: A-metallic base plate 1 has ametallic resilient body 2 in the form of a bellows mounted thereon inusual manner by means of a threaded nut 3. This metallic bellows isconnected through a capillary tube 4 to a fluid feeler 5. The length ofthe capillary tube 4 depends on the size of the boiler. Mounted on saidbase plate 1 is also a small tumbler switch 14 of common design.

I 2,929,991 Patented Mar. 22, 1960 Such tumbler switches usually have arupturing capacity of. l0 a., 250 v. A.C. and are provided with asinglepole change-over contact. Change-over of the contact (not shown)takes place by pressing the tripping pin 6. A transmission lever 7 atone end is pivoted to an axle 8 and supported on the base plate 1 bymeans of a bearing support 9. Said lever 7 has screwed into it anadjusting screw 10 bearing on the upper closing piece 11 of saidbellows. The other end of the lever 7 is pressed by means of a flatspring 12 against the tripping pin 6 with a pressure which is suicientto cause the tumbler switch to change over with certainty, provided thelever 7 is not lifted oc the tripping pin 6 by the pressure of thebellows 2 onto the screw 10. A terminal 13 serves to connect thethermostat electrically, and the whole assembly s closed by a cover ofpressed insulating material.

The action of the thermostat according to Figs. l and 2 is as follows:Metallic bellows 2, feeler 5 and capillary tube 4 are filled with afluid, say, oil, the volume of which changes linearly with thetemperature in the provided temperature range. Thereby, the hollow spaceof the resilient bellows, except the actual folding portion, is filledwith a metallic body so that the bellows itself only takes up a minimumamount of fluid. The oil volume preponderantly is contained in thefeeler 5, whereby the thermostat primarily reacts to the temperature ofthe feeler and not to the temperature of the bellows or capillary tube.As the feeler temperature increases, the resilient' bellows extends,whereby the closing piece 11 presses against the screw 10, raises thelever 7 from the tripping pin 6 and causes the switch 14 to switch oifor over. If, on the other hand, the temperature falls in the feeler 5,the bellows 2 will contract, the lever 7 being thereby moved downwardsunder the action of the spring 12, until it presses against the trippingpin 6 and thus switches the switch on. The switching on or switching-offtemperature can be set by turning the adjusting screw 10.

In the case of boiler therrnostats according to Figs. 1 and 2, thefeeler Snormally is incorporated in a usual type of protective tube. Theeffective length of the feeler may be suited to the conditions from caseto case.

-The thermostat according to Fig. 3, on principle, is constructed of thesame elements 21 to 141 as the boiler thermostat according to Figs. 1and 2; only the casing 16, 17 is adapted to the purpose of applicationof the thermostat, and the transmission ratio of the lever 71 to thetripping pin 61 is chosen greater, in order to obtain highertemperature-sensitivity o-f the regulator. The spring 121 is attached tothe switch lever 71 and presses against an abutment 18 mounted on thetumbler switch 141. The capillary tube 41 extends upwards in Fig. 3, butit may, on principle, also be directed in other directions, say, in thedirection 411.

In a room thermostat, i.e. for regulating the temperature of the room inwhich the thermostat is fitted, the feeler 51 can normally be dispensedwith. ln this case the resilient bellows 21 will be entirely filled withuid so that the ambient temperature of the bellows is decisive for thetemperature regulation.

As small tumbler switches 14, 141, commercially available seriesproducts or specially made types may be used, the only condition beingthat for its operation the switch merely requires a small operating pathof ya few hundredths of a millimeter, which is readily possible instructures with prestres-sed snap-action spring of 'known type. Theprefabricated construction with separate switch unit has moreover theadvantage that the same switch may still be adopted for other purposes,say, as limit switch, control switch, etc. l

` In Figs. 4 and 5, the base plates 11I or 1111 have moutedthereon thequick-break switches 211, 2111. The switches are actuated by trippingpins 311, 3111 having the transmission lever 411,' 4111 bearing thereon.The lever 411 in- Fig. 4 is attachedV to the abutment 611-by means Vof aleaf spring 511 whereas the lever 4111 in Fig. Sis bentand stiiienedfrom the same sheet-iron as its abutment 6111, it being only ofresilient and pliable design at the place 5.111. Each of the levers 411,4111 has screwed therein an adjusting screw 711, 7111 bearing on theresilient bodies 811, 8111 iixed in the base plates 111 and 11I1respectively. The resilient bodies 811, 8111 are iilled with fluid andcommunicate via capillary tubes 911, 9111 with iiuid expansion feelers(not shown).

The springing power of the leaf spring 511 or of the bend 5111 isdimensioned and set so -as to actuate the tumbler switch 211 or 2111with the lever 411, 4111 pressing onto the tripping pin 311, 3111 whenthe adjusting screw 711, 7111 does not engage the resilient body 811,grrr' The action of the thermostat, on principle, is the same as thataccording to Figs. l-3. The uid in the capillary feeler (not shown) issubject to changes in volume in dependence on the temperature, theresilient body 811, 81.11 extending longitudinally or contracts.Movements of the resilient body will be transmitted via screw 711, ,7111to the lever 411, 4111 which actuates the tripping pin' 311, 3111 independence on the temperature at the feeler.

In contradistinction to the arrangement according to Figs. 1 3, noadditional springs whatsoever are required as acting on the lever4114111. At the same time, the bearing by means of knife-edge or rotaryaxle, as usual with levers, is eliminated, thus resulting in anappreciable simplification of the design and a corresponding lowering ofthe cost of manufacture.

'The sensitivity of response of the aforedescribed thermostats withtemperature feelers or resilient bellows of usual size reaches values of0.4 to 2 C. and lies therefore more favorable than in the case of simplethermostats of known designs. For boiler thermostats, on the other hand,a sensitivity of about 3 to 5 C. is deemed suiiicient. Y

This high sensitivity, in conjunction with very. great simplicity of thethermostat, is achieved by the combination of a resilient body with uidexpansion and a small tumbler switch with .very short operating path.The uidfeeler supplies indeed only small expansion values, but on theother hand big switching forces, whereby arswitch with relatively greatswitching power and smallV operating path may be employedY while Vusinga simple transmission lever.

It is understood that with the basic elements set forth still otherthermostatic combinations are possible. A

Fig. 6 shows a further modified form of the` thermostat illustrated inFig. l. The bearing supprt 9 is replaced by a closing piece 91V solderedto a metallic bellows 131V. The latter is iilled withthe same uid, say,oil, as the feeler 51V, the capillary tube;41V and the bellows 21V. Thevolume of the hollow space of the bellows 131Vis of exactly the samesize as that of the bellows 21V.

The action of this compensating thermostat is the same as that accordingto Fig. 1. Since the bellows 21V takes up a minimum amount of jluid, anychange in temperature within the head of the thermostat can influenceits response value; certainly corresponding to the volume ratio betweenthe metallic resilient body'21V and the feeler 51V to an extent that isinferior in order of magnitude than the temperature changes at thefeeler 51V. In certain cases this nuencing of the desired value maycause some disturbance. The `metallic resilient body 131V has for itsduty to equalize the temperature variations within the head of Ythethermostat. Upon increase of the head temperature, the bellows 21V wouldexpand and, without ythe-bellows 131V, -would lift the lever 71V. fromthe tripping pin 61V, thus causing a premature switching of thethermostat. But since also the bellows 131V will then expand in the samesense and to the same extent, any premature lifting of the lever 71Vfrom the tripping pin 61V will be prevented and the response valuerendered purely as dependent on the temperature at the feeler 51V.

In the form according to Figs. 7 and 8, a metallic base plate 1V hasmounted thereon by means of threaded nuts 3V not only one, but tworesilient bodies 2V; turnbler switch EAV, transmission lever 7V,adjusting screw 10V, flat spring 12V being likewise provided induplicate. The axles 8V of the two transmission levers 7V, however, areno longer stationarily arranged with respect to the base plate 1V, butheld in common on a substantially U-shaped carrier 16V. This carrier 16Vis guided on a block 15V and can be displaced vat right angles to thebase plate 1V. Said carrier can be displaced by turning the screw 17Vwhich can be screwed more or less deep into a thread of the block 15V. Acoil spring 18V ensures that said carrier will always be pressed againstthe head of the screw 17V and follow its up and down movements.

The action of the double thermostat according to Figs. 7 and 8 is asfollows: Both thermostats operate individually as described withreference to Figs. 1-3. The switch-on or switch-off temperature may beset individually for each thermostat by turning the adjusting screw 10V.In this way it is possible to have one thermostat set to a certaindesired higher value than the other. By turning the central regulatingscrew 17V both thermostats are adjustable so as to change in both theswitch-on and switch-oi temperature while retaining the temperaturedifference previously set.

The double thermostat according to Figs. 9 and l0 is constructed asfollows: Two thermostats are mounted on a base plate i, together withtwo resilient bodies 2V1 mounted by means of threaded nuts 3171;Vtumbler switch 14V1, transmission lever 7V1, adjusting screw 10171 arelikewise provided in duplicate. The axles 8V1 and 9V1 of the twotransmission levers 711 are not stationarily mounted with respect to thebase plate, but arranged on two carriers 16V1 and IlSVI which aredisplaceable at right angles to said base plate, the carrier 1611 beingguided on the block, and the carrier 18111 on carrier MV1. The up anddown movements of these two carriers are controlled by a screw 17V1,which is guided in a cylindrical bore in the block 15V1 and in the cover19V1. The spring 20W ensures that the screw 1'7V1 lies on the cover19171, to be thus kept vin a xed position' with respect to the baseplate 1v1. The screw 17171 has two threads of different pitches. Onethread has its nut thread within carrier 16W, and the other withincarrier 18W. By turning the screw 17V1 the vertical positions of thecarriers 16V1 and 18V1 will change relative to the base plate inaccordance with the two pitches.

' The action of the double thermostat according to Figs. 9 and l0 is asfollows: Both thermostats operate individually as described withreference to Figs. 1-3. The switch-on and switch-oit temperatures may beset individually by turning the regulating screw 1011. In this way it ispossible to have one thermostat set to a desired higher percentage valuethan the other. By turning the regulating screw 17V1 both thermostatsmay be so adjusted as to simultaneously change in both the switch-on andswitch-off temperatures while maintaining a similar percentagedifference. According to the selection of the ratio of the pitches ofthescrew 17V1, the desired iixed percentage value can be chosen.V Inaccordance with this value, also the rst setting of both thermostatswith the regulating screws 10i/1 must bemade. i

`Although certain preferred embodiments of the present invention havebeen described, it is readily apparent'to oneskilled in the art thatother modications can beV made without departing from thel spirit'ofthe'invention as set forth in the appended claims.

What I claim is:

1. A thermostat, comprising, in combination, a support casing; aresilient bellows mounted in said support casing; a hollow feeler memberlocated outside said support casing; capillary tube means connectingsaid feeler member` to said bellows; a further resilient bellowssubstantially identical with said vbellows mounted in said casing; aliquid filling said feeler member, said tube means, said bellows andsaid further bellows and arranged to move said bellows in response tothethermal expansion and contraction thereof; a lever memberV pivotallymounted on said further bellows and extending over said bellows, saidlever member having a threaded bore opposite said bellows; switch meansmounted in said support casing; spring means mounted in said supportcasing and urging said lever member against said switch means; threadedspacing means mounted in said bore of said lever member and having anend portion spaced from said bellows at an adjustable distance, wherebysaid bellows will engage said spacing means to turn said lever memberagainst the bias of said spring means away from said switch means foractuating the same when said bellows moves in response to the expansionof said fluid and whereby the movement of said bellows is partlycompensated lby the movement of said further bellows.

2. A thermostat comprising, in combination, a support member; a firstresilient bellows mounted on said support member; a hollow feeler memberlocated outside said'support member; tube means connecting said feelermembers to said first bellows, to. form an interconnected first bellowsassembly; a second resilient bellows mounted on said casing; a fiuidfilling the said second bellows and filling said first bellows assembly,said liquid being arranged to move said first and secondy bellows inresponse to the thermal expansion and contraction thereof; a levermember pivotally mounted on said secondl bellows and extending over saidfirst bellows, said lever member including threaded bore opposite saidfirst bellows; switch means mounted on said support member; spring meansmounted on said support `member and urging said lever member againstsaid switch means; threaded spacing means mounted in said bore of saidlever member and having an end portion spaced from said first bellows atan adjustable distance, whereby said bellows will engage said spacingmeans to turn said lever member against the bias of said spring meansaway from said switch means for actuating the same when said bellowsmove in response to the expansion of said fluid in said first bellowsassembly, and whereby the movement of said first bellows is partlyVcompensated by the movement of said second bellows due t the thermalexpansion of said fiuid therein.`

3. A thermostat comprising, in combination. a support member; aplurality of resilient bellows mounted on said support member; aplurality of hollow feeler members located outside said support member;capillary tube means connecting one of said bellows with one o-f saidhollow feeler members to form a plurality of interconnected bellowsassemblies; a liquid filling each of said bellows assemblies; aplurality of lever means pivotally supported on said support member, oneof said levers extending over one of said bellows at a selecteddistance, said lever means including each a threaded bore opposite oneof said bellows; a plurality of switch means mounted on said supportmember, one switch means associated with one of said bellows assemblies;spring means mounted on said support member and urging said levermembers against said switch means; threaded spacing means mounted insaid bore of each of said levers and have an end portion spaced fromeach of said bellows at an adjustable distance, whereby said bellowswill selectively engage said spacing means to turn one of said levermembers against the bias of said spring means away from saidv switchmeans for actuating the same when said' bellows move in response to theexpansion of said fluid'.

4. A thermostat comprising, in combination, a support member; aplurality of resilient bellows mounted on said support member; aplurality of hollow feeler members located outside said support member;capillary tube means connecting one of said bellows with one of saidhollow feeler members to form a plurality of interconnected bellowsassemblies; a support element mounted on said support member andextending longitudinally of said bellows; means mounted on said supportmember for selectively adjusting the position of said support elementlongitudinally of said bellows; a plurality of lever means pivotallysupported on said supportelement, one of said levers extending over oneof said bellows at a selected distance, said lever means including eacha threaded bore opposite one of said bellows; a plurality of switchmeans mounted Aon said support member, one switch means associated withoneV of said bellows assemblies; spring means mounted on` said supportmember and urging said lever members against said switch means; threadedspacing means mounted in said bores of each of said levers and having anend portion spaced from each of said bellows at an adjustable distance,whereby said bellows will selectively engage said spacing means to turnone of said lever members against the bias of said spring means awayfrom said switch means for actuating the same when said bellows move inresponse to the expansion of said fiuid, and whereby said distancebetween said levers on said bellows can be adjusted.

5. A thermostat comprising, in combination, a support member; a firstresilient bellows mounted on said support member; a first hollow feelermember located outside said support member; first tube means connectingsaid first bellows with said first feeler member to form a firstinterconnected bellows assembly; a second resilient bellows mounted onsaid support member; a second hollow feeler member located outside saidsupport member; second tube means connecting said second bellows withsaid second feeler member to form a second interconnected bellowsassembly; a liquid filling said first bellows assembly and said secondbellows assembly; first switch means mounted on said support member andcooperating with said first bellows assembly; second switch meansmounted on said support member and cooperating with said second bellowsassembly; a support element mounted on said support member and extendinglongitudinally of said first and said second bellows; means mounted onsaid support member for selectively adjusting the position of saidsupport element longitudinally of said bellows; first lever meanspivotally supported on said support element and extending over saidfirst bellows at a selected distance and including a threaded boreopposite said first bellows; second lever means pivotally supported onsaid support element and extending over said second bellows at aselected distance and including a threaded bore opposite said secondbellows; first threaded spacing means mounted in said bore of said firstleve-r means and having an end portion spaced from said first bellows atan adjustable distance; second threaded spacing means mounted in saidbore of said second lever means and having an end portion spaced fromsaid second bellows at an adjustable distance; spring means mounted onsaid support member and urging said first lever member and said secondlever member against said first switch means and said second switchmeans, respectively, whereby said means can be actuated to alter thedistance between said first levers and said first bellows and betweensaid second lever means and said second bellows, and whereby saidbellows will selectively engage said spacing means to turn said firstand said second lever members against the bias of said spring means awayfrom said first and second switch means, respectively, for actuating thesame when said first and second bellows move in response to theexpansion of said fiuid.

`6.Y A thermostat comprising, in combination, a support member; a firstresilient bellows mounted on said support member; a first hollow feelermember located outside said support member; first tube means connectingsaid first bellows with said first feeler member to form a firstinterconnected bellows assembly; a second resilient bellows mounted onsaid support member; a second hollow feeler member located outside saidsupport member; second tube means connecting said second bellows withsaid second feeler member to form a second interconnected bellowsassembly; a liquid filling said first bellows assembly and said secondbellows assembly; first switch'means mounted on said support member andcooperating with said first bellows assembly; second switch meansmounted on said support member and cooperating with said second bellowsassembly; a support element mounted on said support member and extendinglongitudinally of said first and said second bellows and including afirst pivot means and a second pivot means; means mounted on saidsupport member for selectively adjusting the position of said supportelement longitudinally of said bellows; first lever means pivotallysupported on said first pivot means of said support elementand extendingover said first bellows at a selected distance and including a threadedbore opposite said first bellows; second lever means pivotally supportedonsaid second pivot means of said support element andextending over saidsecond bellows at a selected distance and including a vthreaded boreopposite said second bellows; first threaded spacing means mounted insaid bore of said first lever means and having an end portion spacedfrom said first bellows at an adjustable distance; second threadedspacing means mounted in said bore of said second lever means and havingan end portion spaced from said second bellows at an adjustabledistance; spring means mounted on said support member and urging saidfirst lever member and said second lever member against said firstswitch means and said second switch means, respectively, whereby saidmeans can be actuated to alter the distance between said first leversand said first bellows and between said second lever means and saidsecond bellows, and whereby said bellows will selectively engage saidspacing means to turn said first and said second lever members againstthe bias of said spring means awayfrom said firsttandtsecond switchmeans, respectively, for actuating' the same when said first and secondbellows move in responseto the expansion of said fiuid.

7. A thermostat comprising, in combination, a support member; a rstresilient bellows mounted on said support member; a first hollow feelermember located outside said support member; rst tube means connectingsaid first bellows with said first feeler member to form a firstinterconnected bellows assembly; a second resilient bellows mounted onsaid support member; a second hollow feeler memberllocated outside saidsupport member; second tube means connecting said second bellows withsaid second feeler member to form a second interconnected bellowsassembly; a liquid filling said first bellows assembly and said secondbellows assembly; first switch means mounted on said support member andcooperating with said first bellows assembly; second switch meansmounted on said support member and cooperating with said second bellowsassembly; a support element mounted on said support member and extendinglongitudinallyof said first and said second bellows and includingrafirst pivot means and a second pivot means; means mounted on saidsupport member for differentially adjusting the position of said firstand second pivot means longitudinally of said bellows; first lever meanspivotally supported on said first pivot means of said support elementand extending over said first bellows at a selected distance andincluding a threaded bore opposite said first bellows; second levermeans pivotally supported on said second pivot means of said supportelement and extending over said second bellows at a selected distanceand including a threaded bore opposite said second bellows; firstthreaded spacing means mounted in said bore of said first lever meansand having an end portion spaced from said first bellows at anadjustable distance; second threaded spacing means mounted in said boreof said second lever means and having an end portion spaced from saidsecond bellows at an adjustable distance; spring means mounted on saidsupport member and urging said first lever member andl said second levermember against said first switch means and said second switch means,respectively, whereby said means can be actuated to alter the distancebetween said first levers and said first bellows and between said secondlever means and said second bellows, and whereby said bellows willselectively engage said spacing means to turn said first and said secondlever members against the bias of said spring means away from said firstand second switch means, respectively, for actuating the same when saidfirst and second bellows move in response to the expansion of saidfiuid.

References Cited in the file of this patent UNITED STATES PATENTS2,274,329 Hammond Feb. 24, 1942 2,355,975 Henrici Aug. 15, 19442,727,115 Visser et al. Dec. 13, 1955 2,758,178 Eskin Aug. 7, 1956'2,792,475 Sweger May 14, 1957 2,828,373 Sweger Mar. 25, 1958

